Currently, the liquid crystal display device has been widely used as a display component of electronic devices in various electronic products. The GOA (Gate Driver On Array) circuit is an important part of a liquid crystal display device. The GOA circuit is a technique using the existed process of manufacturing thin film transistor liquid crystal display array to manufacture a gate line scan driving signal circuit on an array substrate to realize a driving method scanning each gate line in sequence.
In accordance with TFT (Thin Film Transistor) type used in a display panel, the display panel based on LTPS (Low Temperature Poly-silicon) technique could be divided into NMOS type panel, PMOS type panel and CMOS type panel having both NMOS type and PMOS type. Similarly, the GOA circuit is divided into NMOS circuit, PMOS circuit and CMOS circuit. Comparing with the CMOS circuit, the NMOS circuit is helpful in increasing yield rate and decreasing cost because masks and procedures for manufacturing a PP (P doping, or Phosphorus ion doping) layer could be saved. Therefore, development of a stable NMOS circuit is a realistic need of this industry. When power is turned off abnormally and the NMOS type GOA circuit cannot effectively achieve the function of All Gate ON (that is, setting all the gate driving signals in the GOA circuit to be enabled to simultaneously scan the liquid crystal display panel), image sticking occurs on the display panel.
Taking forward scanning as an example and assuming that the (n+1)th clock signal received by the TFT NT3 is at high potential at the time when abnormal power off occurs in the GOA circuit shown in FIG. 1, the forward scan control signal and the (n+1)th clock signal are simultaneously pulled down to a low potential so that the high potential at the gate of the TFT NT5 cannot be released and therefore the TFT NT5 is kept at turned-on status. At the same time, the TFT NT8 is also in the turned-on status so that the gate of the TFT NT7 cannot be fully pulled down due to overlapping of the high potential signal VGH and the low potential signal VGL. Therefore, the gate driving signal G(n) output from the TFT NT7 to the TFT of the pixel unit is pulled down and is not enough for turning on the TFT of the pixel unit. Accordingly, the charges in the pixel electrode cannot be released in time, and image sticking in the effective displaying area is therefore generated due to abnormal power off.